This invention relates to analyzers for internal combustion engines and in particular, to a new and improved timing indicator for an engine ignition analyzer.
The ignition analyzers utilizing a cathode ray oscilloscope display are well known and widely used by mechanics in obtaining information regarding the performance of internal combustion engines. Typically the horizontal sweep of the oscilloscope trace is initiated by the engine ignition pulse and the trace is deflected vertically during the sweep as a function of the voltage of the ignition coil. Present day analyzers provide various displays with various inputs for developing a wide range of information useful to the mechanic.
The sweep time of the horizontal axis of the oscilloscope trace is determined by the engine speed and therefore the actual time of a sweep is variable and not readily determined. For certain types of analysis, the mechanic needs to know the actual duration of time during which a spark plug is ionized or firing. With the conventional ignition analyzer, the mechanic can determine whether one spark plug has a longer or shorter ionization time than the other plugs. However in some instances all firing cycles will be uniform but short in duration, such as when the coil is weak, and this condition cannot be determined by comparison of one plug firing cycle with that of another.
In some prior art analyzers, timing lines are permanently provided on the face of the oscilloscope so that when the engine is operated at a predetermined speed, the spacing between the fixed timing lines will represent known time intervals. However this has not bee a satisfactory resolution of the problem, since it requires operation of the engine at a predetermined constant speed.
It is an object of the invention to provide new and improved method and apparatus for producing real time indications in an ignition analyzer oscilloscope trace where the sweep time of the trace varies with engine speed. A further object is to provide such method and apparatus wherein the time indications comprise markers in the trace, with the intervals between the markers representing predetermined time periods, typically one millisecond. An additional object is to provide such method and apparatus where the markers may be high intensity spots in the trace or gaps in the trace, as desired. A specific object is to provide such method and apparatus wherein the time interval between the engine ignition pulse and the first marker is the same as the time intervals between succeeding markers.